Correspondences
What is linked, what is not
Each arc joins two phenomena tested on this site. Green and animated: clear link (correlation significant at 5 % after correcting for autocorrelation, or a response outside chance in an event study). Grey: inconclusive test. A statistical link alone does not establish causation.
- Clear link
- Inconclusive
Hypotheses tested
16
Clear links
11
Causation demonstrated
0
Arc width from |r| of the stored result; several tests between the same phenomena are drawn as stacked arcs.
Hypothesis tested: El Niño strengthens the upper-level westerlies over the Caribbean and the tropical Atlantic. The resulting vertical wind shear tears storms apart: El Niño seasons should be less active, La Niña seasons more active (Gray, 1984; Klotzbach, 2011).
Pearson correlation r (lag 0 year(s))
-0.35
95% interval [-0.54; -0.15] (block bootstrap)
Aligned points
76
effective n ≈ 76 (autocorrelation)
p-value
0.002
two-sided, Fisher z transform, effective n
Mean ACE, El Niño seasons
86 10⁴ kt²
20 seasons
Mean ACE, neutral seasons
105 10⁴ kt²
38 seasons
Mean ACE, La Niña seasons
136 10⁴ kt²
18 seasons
Period analysed
1950 → 2025
computed on Oct 23, 2026 · engine v1.0
Aligned series (standard deviations, after preprocessing)
Show the data as a table
Correlation by lag (year(s))
Show the data as a table
Method and sources
The ONI of the August–September–October season (value centred on September, CPC) is compared with the season’s ACE in HURDAT2, from 1950 to the last complete season. The lag is fixed at zero a priori (same season). The confidence interval comes from a 3-year block bootstrap (1,000 draws). Seasons are classed El Niño (ONI ≥ +0.5 °C), La Niña (≤ −0.5 °C) or neutral.
Computation parameters
{
"x": "ONI of August–October (CPC, ERSSTv5)",
"y": "North Atlantic ACE of the season (HURDAT2), 10^4 kt²",
"lag": "fixed at 0 (same season)",
"el_nino": "ONI ≥ +0.5 °C",
"la_nina": "ONI ≤ −0.5 °C",
"bootstrap": {
"seed": 20261023,
"block": 3,
"draws": 1000
},
"from_year": 1950
}Inputs : cpc.oni.monthly (920 pts, run #13) · hurdat2.ace.yearly (175 pts, run #21)
Reading this result
The correlation is negative and clear, but ENSO explains only part of the variability: the Atlantic itself (surface temperature, AMO) and the chance of each season matter as much. An El Niño season can stay active, like 2023 with a record-warm Atlantic. Correlation is not causation: common factors (seasons, cycles, trends) or coincidence can produce it. The p-values account for autocorrelation (effective n) but not for preprocessing choices; the confidence interval comes from a block bootstrap. The limits of the source data apply.
SOURCES OF THIS PAGE
- Oceanic Niño Index (NOAA CPC)
-
NOAA CPC, Oceanic Niño Index (ONI): 3-month running mean of ERSSTv5 SST anomalies in the Niño 3.4 region, centred 30-year base periods updated every 5 years.
· source page ↗
Licence : U.S. Government work, public domain · retrieved on Oct 23, 2026 · SHA-256 5d6fa3a2f857… - HURDAT2 Atlantic hurricane database (NOAA NHC)
-
Landsea, C. W., Franklin, J. L. (2013). Atlantic hurricane database uncertainty and presentation of a new database format. Monthly Weather Review 141, 3576–3592 (HURDAT2, NOAA NHC).
· doi:10.1175/MWR-D-12-00254.1 · source page ↗
Licence : U.S. Government work, public domain · retrieved on Oct 23, 2026 · SHA-256 75202780ce56… - Gray (1984)
-
Gray, W. M. (1984). Atlantic seasonal hurricane frequency. Part I: El Niño and 30 mb quasi-biennial oscillation influences. Monthly Weather Review, 112(9), 1649–1668.
· doi:10.1175/1520-0493(1984)112<1649:ASHFPI>2.0.CO;2
Licence : Published literature; cited - Klotzbach (2011)
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Klotzbach, P. J. (2011). El Niño–Southern Oscillation’s impact on Atlantic basin hurricanes and U.S. landfalls. Journal of Climate, 24(4), 1252–1263.
· doi:10.1175/2010JCLI3799.1
Licence : Published literature; cited